The present invention relates to pens for ink-jet printers and, more particularly to a protective cover apparatus for such pens.
A pen for an ink-jet printer includes a reservoir for containing a supply of ink and a print head having an array of minute orifices that are shaped as nozzles through which ink drops are ejected. Thermal resistors or piezoelectric mechanisms associated with each nozzle are responsive to electrical signals for generating drops that are selectively ejected to form images on paper that is advanced through the printer. When the pen is positioned within a printer carriage, electrical contacts on the pen engage corresponding contacts on the printer carriage to allow electrical connection of the drop generators with the control system of the printer.
Ink pens are replaceable so that when the supply of ink within the reservoir is depleted or the print head malfunctions, the pen can be removed and replaced with a new pen.
Unless protected, the orifices of the print head can become plugged as a result of the accumulation of dust or paper fibers on the print head. Such foreign particles may accumulate on an exposed print head.
Vapor loss may also cause an ink pen to malfunction. Ink is a combination of many different components, some of which evaporate more readily than others. As a result, prolonged exposure of the ink to the ambient atmosphere will cause the evaporation of at least the most readily evaporated components. This evaporation can alter the composition of the ink such that the pen can no longer function properly. In extreme cases, the ink within the orifices may thicken or solidify, thereby plugging the orifices.
To ensure the reliable and efficient operation of an ink-jet pen, it is desirable to protect the print head orifices to the extent practical. The print head of some ink pens may be covered with tape following the manufacture of the pen. The tape serves as a vapor barrier to limit evaporation of the ink and covers the print head to help prevent contamination of the print head during shipment and storage of the ink pen. The tape is removed and discarded prior to placing the ink pen within a printer. As a result, the print head and ink-jets may be left unprotected and without an adequate vapor barrier during the life of the ink pen.
Some ink-jet printers are provided with built-in capping stations. When the ink pen is not printing, the printer moves the ink pen to the capping station where the print head and ink-jets are shielded. However, over time such permanent capping stations can become dirty or wear out. If this occurs, the capping stations no longer perform properly and moving an ink pen to such a capping station may contribute to the contamination of the print head. Furthermore, built-in capping stations may contact the orifices on the print head if either the capping station or the ink pen is slightly misaligned within the printer. Such contact can push paper dust and spattered ink into the orifices, thereby plugging the orifices.
Special storage containers, or ink pen garages, are also available to protect ink pens. However, when an ink pen garage is used for protection, the ink pen must be removed from the printer, placed in the ink pen garage, and then removed from the garage and replaced within the printer for use.